peer-reviewed) is the author/funder. All rights reserved. No reuse allowed without permission.The copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/217968 doi: bioRxiv preprint first posted online Nov. 11, 2017; 3 To understand how Seb1 interfaces with the transcription of dg and dh repeats to promote heterochromatin, we employed a previously identified viable, heterochromatindefective allele, seb1-1 15 . When combined with mutants in the RNAi machinery, seb1-1 eliminates pericentromeric heterochromatin, while the corresponding single mutants decrease H3K9me, indicative of partially redundant pathways 15 . We examined transcription of heterochromatin at single-nucleotide resolution and tested the impact of the seb1-1 allele using Nascent Elongating Transcript Sequencing (NET-Seq) 20 . To analyze the intrinsic transcriptional properties of heterochromatic sequences prior to the establishment of heterochromatin assembly, we used the clr4∆ mutant, which lacksH3K9me and displays full derepression of most silenced chromatin regions. We compared this strain to a clr4∆ seb1-1 double mutant to assess the impact of seb1-1.We first examined the effect of seb1-1 on transcription of non-heterochromatic regions peer-reviewed) is the author/funder. All rights reserved. No reuse allowed without permission.The copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/217968 doi: bioRxiv preprint first posted online Nov. 11, 2017; 4 Extended Data Figure 1). The seb1-1 mutation causes a reduced median 5' traveling ratio and an increased median 3' traveling ratio for both clusters ( for p values). These data indicate that the seb1-1 allele leads to decreased RNAPII pausing at gene 5' ends with an associated increased 3' signal; the latter may be due to polymerase release from upstream pauses. peer-reviewed) is the author/funder. All rights reserved. No reuse allowed without permission.The copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/217968 doi: bioRxiv preprint first posted online Nov. 11, 2017; 5 To compare the binding of Seb1 across transcript classes, we computed the fraction of RNA covered by Seb1 PAR-CLIP read clusters. We observed a ~12-fold higher PAR-CLIP cluster coverage for pericentromeric repeat intervals than for coding gene intervals (Figure 2d and Extended Data Figure 4a). Non-coding RNAs display the highest coverage at a mean level ~100-fold higher than that of coding-genes (Extended Data Figure 4b).We next examined the NET-Seq profiles of pericentromeric heterochromatin sequences of clr4∆ and clr4∆ seb1-1 strains (replicate experiments were conducted). The copyright holder for this preprint (which was not . http://dx.doi.org/10.1101/217968 doi: bioRxiv preprint first posted online Nov. 11, 2017; 6 Figure 4d).These data reveal detectable Seb1-dependent RNAPII pauses in pericentromeric sequences. (Figure 2g). Silencing of ura4 + was determined using YS-FOA plates, which selects for ura4+ repression. The insert of Fragment ...